A multiple-antenna system is a system where a transmitting end or both a transmitting end and a receiver use multiple antennas for transmission or reception. A multiple-antenna technology utilizes the spatial channel characteristics provided by the multiple-antenna system to implement better utilization of spatial channels by using proper forms of transmit signals and receiver designs under different operating scenarios, thus increasing system capacity or enhancing transmission reliability. It has been proved that the multiple-antenna technology may achieve many different types of transmission gains without increasing the total transmit power. Based on the foregoing advantages, the multiple-antenna technology has been widely applied in many communication systems such as High Speed Packet Access, HSPA, Long Term Evolution, LTE, and Worldwide Interoperability for Microware Access, WiMAX.
However, the introduction of multiple-antenna technology gives rise to additional costs. Generally, each receive and transmit antenna is connected to a radio frequency channel which includes radio frequency circuit modules such as a power amplifier and a filter. From the perspective of energy consumption, the energy consumption of the radio frequency channels accounts for over 50% of the energy consumption of a radio base station as a whole. Even if no data is transmitted, the static power consumption for maintaining the normal operating state of radio frequency devices in the radio frequency channels still needs a high power consumption overhead. Therefore, in the multiple-antenna system, because the number of radio frequency channels is increased, the power consumption caused by the radio frequency channels is also increased accordingly, and finally, the power consumption of the base station as a whole is increased. How to decrease the power consumption in the multiple-antenna system without affecting quality of service is a pressing issue currently.
In the prior art, a method for decreasing power consumption in a multiple-antenna system is using an antenna switched diversity technology. The antenna switched diversity technology means that when there are multiple transmit antennas on the transmitting end, one of the antennas is selected according to a certain sequence in time or frequency for transmission. If the antennas are switched on different subcarriers, it is known as frequency switched transmit diversity (Frequency Switched Transmit Diversity, FSTD); and if the antennas are switched at different time, it is known as time switched transmit diversity (Time Switched Transmit Diversity, TSTD). FIG. 1 is a schematic structural diagram of an antenna switched diversity technology used in a multiple-antenna system for transmitting data in the prior art. In this method, at each determined time or determined frequency, the number of antennas that are turned on is fixed, and for the multiple-antenna system, using the fixed number of antennas to transmit data may inevitably affect the dynamic transmission performance of the system, such as a packet loss rate or a retransmission rate.
Another way of decreasing power consumption in a multiple-antenna system is to reduce the number of transmit antennas, thus turning off some frequency channels. The specific method is as follows: according to current service needs and service change regularity of a time period, the base station of each cell determines the number of transmit antennas to be used for the cell for the next time period; the base station sends a message to all terminals in the cell to notify that the number of transmit antennas is changed; and after receiving the message of notification, the terminals perform corresponding configuration. In the process of implementing this method in an LTE system, because different numbers of transmit antennas correspond to different CRC masks, after a terminal configures a wrong number of transmit antennas, a wrong PBCH CRC mask may be used at the time of CRC decoding, thus leading to a CRC check failure. In order to ensure that the terminal does not make a mistake in configuring the number of transmit antennas, there should be corresponding measures to ensure that the terminal currently acquires the correct number of transmit antennas, which needs an additional scheme design and signaling design, thus inevitably causing an additional signaling overhead and processing delay.
Furthermore, for the terminal itself, the protocol of the terminal needs to be changed; in addition, with respect to different types of terminals, different design schemes need to be used. Therefore, the implementation complexity is also increased.